Detergent composition



United States Patent 3,407,144 DETERGENT COMPOSITION David Frank Bath, Northumberland, England, assignor to The Procter & Gamble Company, Cincinnati, Ohio,

a corporation of Ohio No Drawing. Filed Dec. 2, 1964, Ser. No. 415,478 Claims priority, application Great Britain, Dec. 11, 1963,

1 Claim. (Cl. 252 108) ABSTRACT OF THE DISCLOSURE A three-layer detergent briquette which is readily and quickly soluble in water, and which has outer layers that are relatively smooth and abrasion resistant.

This invention relates to detergent briquettes and to a method of manufacture of such briquettes. The term briquettes is used to include tablets.

In household use, and particularly for use in domestic washing machines, a convenient form of detergent composition is the detergent briquette. By adding the required number of briquettes of uniform weight to the washing machine, a standard amount of detergent can be added without the use of'measuring vessels such as are recommended for powder or liquid detergent compositions.

Such detergent briquettes must disintegrate quickly and dissolve rapidly when added to water. They must also be resistant to abrasion and accidental breakage and the formation of dust, for example during transport when the briquettes are packed together in a container.

Detergent briquettes of low time of disintegration (T.O.D.), which produce lather rapidly when added to water in a washing machine, can be obtained from a dry particulate mixture of inorganic builder salts and synthetic detergent and/or soap; with this mixture may optionally be mixed a small amount of a binding agent such as water, sodium silicate solution or aqueous suspension of starch, for example by spraying such binding agent onto the dry particulate mixture. The mixture is compressed into briquette form. Such briquettes may have a low T.O.D., but they have a rough surface which is not pleasant to handle and has low resistance to abrasion, so that the surface is frequently dusty and leaves dust on the fingers when the briquettes are handled. Attempts have been made to overcome this difficulty by coating the briquettes with a Water-soluble film-forming substance such as polyvinyl alcohol but this has its own inherent disadvantages. The T.O.D. is increased because the water-soluble film must be dissolved before the briquettes can disintegrate, the film tends to become sticky and unpleasant on accidental contact with liquid water or on storage in a humid atmosphere, and the process is costly.

Detergent briquettes which have a smooth surface which is pleasant to handle and is resistant to abrasion and consequent formation of dust, can be produced by compressing conventional spray-dried built detergent granules into tablet form. Such briquettes, however, have a longer T.O.D. than the previously described briquettes.

It has now been found that detergent briquettes which have a smooth surface with high resistance to abrasion and the formation of dust, and which also have a low T.O.D. and produce lather rapidly on addition to water in a washing machine, can be prepared in the form of a threelayer briquette in which the outer layers comprise one or more functional ingredients of the detergent briquette which, on compression, produce a smooth abrasion resistant surface, and the inner layer comprises a mixture of 3,407,144 Patented Oct. 22, 1968 particulate inorganic builder salts and a particulate detergent composition which mixture, on compression, would normally produce a rough surface which is readily abraded.

By functional ingredient of the detergent briquette is meant an ingredient of the total composition of the briquette which makes a positive contribution to the washing and cleaning action of the briquette in use. Thus, the active detergent ingredient itself, whether this be soap or a synthetic detergent, is a functional ingredient; so also are lather and .detergency enhancing agents, soil suspending agents, lime sequestering agents, bleaching agents and other materials which take part in the washing and cleaning action. Filling agents or inert diluents are not functional ingredients.

Accordingly, this invention provides a detergent briquette consisting of three layers, the first and third layers being outer layers each comprising a compressed material which itself comprises one or more functional ingredients of the detergent briquette and which, on compression, produces a relatively smooth, abrasion resistant surface,

and the second layer being an inner layer comprising a built detergent composition which is a mixture of one Or more particulate inorganic builder salts and a particulate detergent composition, and which would produce, if compressed alone, a rougher and more easily abraded surface than that produced by either of the outer layers, the mixture being produced in the absence of liquid or in the presence of insufficient liquid to destroy the particulate nature of the mixture, the second layer constituting at least 50%, by weight, of the briquette.

. The invention also provides a method of producing a detergent briquette in which there is placed in the die box of a briquetting press a first layer, comprising a material Which itself comprises one or more functional ingredients of the detergent briquette and which, on compression, will produce a relatively smooth, abrasion resistant surface; there is superimposed on the first layer a second layer comprising a built detergent composition which is a mixture of one or more particulate inorganic builder salts and a particulate detergent composition, and which would produce, if compressed alone, a rougher and more easily abraded surface than that produced by either the first or the third layer, the mixture being produced in the absence of liquid or in the presence of insufficient liquid to destroy the particulate nature of the mixture; there is superimposed on the second layer a third layer comprising a material which itself comprises one or more functional ingredients of the detergent briquette and which, on compression, will produce a relatively smooth, abrasion resistant surface; and the three layers are compressed together to form a briquette of which the second layer constitutes at least 50%, by weight. To give the briquette an attractive appearance, it is possible to have the layers of different colours. Conveniently, the first and third layers may have the same composition.

The material of the outer layers must, on compression, produce a relatively smooth, abrasion resistant surface. By abrasion resistant is meant having a reduced tendency to form dust, for example when the briquettes are handled or packed together in cartons for transport.

' The outer layers of the briquette may be different from each other, but are preferably the same. They may comprise a material comprising any of the functional ingredients of the detergent briquette which, on compression, produces a smooth, abrasion resistant surface. The material is preferably in the form of flakes, granules or powder. For example, material of the outer layers may comprise soap, concentrated synthetic detergent, fatty acid amides or alkylolamides, fatty alcohol, fatty acid or a mixture of any of these.

Examples of detergent materials which can be used include:

(1) Ordinary alkali metal soaps such as the sodium and potassium salts of the higher fatty acids of naturally occurring plant or animal esters (e.g., palm oil, coconut oil, babassu oil, soybean oil, castor oil, tallow, whale and fish oils, grease and lard, and mixtures thereof) or of synthetically produced fatty acids (e.g., rosin and those resin acids in tall oils) and/or of naphthenic acids. Sodium and potassium soaps can be made by direct saponification of the fats and oils or by the neutralization of the free fatty acids which are prepared in a separate manufacturing process.

(2) Synthetic organic detergents characterized by their high solubility in water, their resistance to precipitation by the constituents of hard water and their surface active and effective detergent properties, including:

(a) Anionic synthetic detergents (excluding true soaps): This class of synthetic detergents can be broadly described as the water-soluble salts, particularly the alkali metal salts, of organic sulfuric reaction products having in the molecular structure an alkyl radical containing from about 8 to about 22 carbon atoms and a radical selected from the group consisting of sulfonic acid and sulfuric acid ester radicals. Important examples of the synthetic detergents which form a part of the preferred compositions of the present invention are the sodium or potassium alkyl sulfates, especially those obtained by sulfating the higher alcohols produced by reducing the glycerides of tallow or coconut oil; sodium or potassium alkyl benzene sulfonates, in which the alkyl group in a straight or branched chain contains from about 9 to about 15 carbon atoms, particularly straight chain sodium dodecyl benzene sulfonate and the types described in United States Letters Patent Numbers 2,220,099 and 2,477,383; sodium alkyl glyceryl ether sulfonates, especially those ethers of the higher alcohols derived from tallow and coconut oil; sodium coconut oil fatty acid monoglyceride sulfates and sulfonates; sodium or potassium salts of sulfuric acid esters of the reaction product of one mole of a higher fatty alcohol (e.g., tallow or coconut oil alcohols) and about three moles of ethylene oxide; sodium or potassium salts of alkyl phenol ethylene oxide ether sulfates with an average of about four units of ethylene oxide per molecule and in which the alkyl radicals contain about 9 carbon atoms; the reaction product of fatty acids esterified with isethionic acid and neutralized with sodium hydroxide where, for example, the fatty acids are derived from coconut oil; sodium or potassium salts of fatty acid amide of a methyl taurine in which the fatty acids, for example, are derived from coconut oil; and others known in the art, a number being specifically set forth in United States Letters Patent Numbers 2,486,921, 2,486,922 and 2,396,278.

(b) Nonionic synthetic detergents: This class of synthetic detergents can be broadly defined as compounds produced by the condensation of alkylene oxide groups (hydrophilic in nature) with an organic hydrophobic compound, which can be aliphatic or alkyl aromatic in nature. The length of the hydrophilic or polyoxyalkylene radical which is condensed with any particular hydrophobic group can be readily adjusted to yield a watersoluble compound having the desired degree of balance between hydrophilic and hydrophobic elements.

For example, a well known class of nonionic synthetic detergents is made available on the market under the trade name of Pluronic. These compounds are formed by condensing ethylene oxide with a hydrophobic base formed by the condensation of propylene oxide with propylene glycol. The hydrophobic portion of the molecule which, of course, exhibits water insolubility has a molecular weight of from about 1500 to 1800. The addition of polyoxyethylene radicals to this hydrophobic portion tends to increase the water solubility of the molecule as a whole and the liquid character of the products is retained up to the point where polyoxyethylene content is about 50% of the total weight of the condensation product.

Other suitable nonionic synthetic detergents include:

(i) The polyethylene oxide condensates of alkyl phenols, e.g., the condensation products of alkyl phenols having an alkyl group containing from about 6 to 12 carbon atoms in either a straight chain or branched chain configuration, with ethylene oxide, the said ethylene oxide being present in amounts equal to 10 to 25 moles of ethylene oxide per mole of alkyl phenol. The alkyl substituent in such compounds may be derived from polymerized propylene, diisobutylene, octane, or nonane, for example.

(ii) Those derived from the condensation of ethylene oxide with the product resulting from the reaction of propylene oxide and ethylene diamine-products which can be varied in composition depending upon the balance between the hydrophobic and hydrophilic elements which is desired. For examples, compounds containing from about 40% to about polyoxyethylene by weight and having a molecular weight of from about 5000 to about 11,000, resulting from the reaction of ethylene oxide groups with a hydrophobic base constituted of the reaction product of ethylene diamine and excess propylene oxide, said base having a molecular weight of the order of 2500 to 3000, are satisfactory.

(iii) The condensation products of aliphatic alcohols having from 8 to 18 carbon atoms, in either straight chain or branched chain configuration, withethylene oxide, e.g., a coconut alcohol ethylene oxide condensate having from 10 to 30 moles of ethylene oxide per mole of coconut alcohol, the coconut alcohol fraction having from 10 to 14 carbon atoms.

(c) Long chain tertiary amine oxides corresponding to the following general formula, R R R N O, wherein R is an alkyl radical of from about 8 to about 18 carbon atoms, and R and R are each methyl or ethyl radicals. The arrow in the formula is a conventional representation of a semi-polar bond. Examples of amine oxides suitable for use in this invention include dimethyldodecyl amine oxide, dimethyloctylamine oxide, dimethyldecylamine oxide, dimethyltetradecylamine oxide, dimethylhexadecylamine oxide.

(d) Long chain tertiary phosphine oxides corresponding to the following general formula RRRP- O wherein R is an alkyl, alkenyl or monohydroxyalkyl radical ranging from 10 to 18 carbon atoms in chain length and R' and R" are each alkyl or monohydroxyalkyl groups containing from 1 to 3 carbon atoms. The arrow in the formula is a conventional representation of a semi-polar bond. Examples of suitable phosphine oxides are:

dodecyldimethylphosphine oxide, tetradecyldimethylphosphine oxide, tetradecylmethylethylphosphine oxide, cetyldimethylphosphine oxide, stearyldimethylphosphine oxide, cetylethylpropylphosphine oxide, dodecyldiethylphosphine oxide, tetradecyldiethylphosphine oxide, dodecyldipropylphosphine oxide,

dodecyldi (hydroxymethyl) phosphine oxide dodecyldi (Z-hydroxyethyl) phosphine oxide, tetradecyImethyI-Z-hydroxypropyl phosphine oxide, oleyldimethylphosphine oxide, and 2-hydroxydodecyldimethylphosphine oxide.

(e) Long chain dialkyl sulfoxides containing one short chain (usually methyl) and one long hydrophobic chain which can contain from about 10 to about 20 carbon atoms. Examples include:

octadecyl methyl sulfoxide dodecyl methyl sulfoxide tetradecyl methyl sulfoxide (f) Ampholytic synthetic detergents can be broadly described as derivatives of aliphatic secondary and tertiary amines in which the aliphatic radical can be straight chain or branched and wherein one of aliphatic substituents contains from about 8 to about 18 carbon atoms and one contains an anionic water solubilizing group, e.g., carboxy, sulfonate, sulfate, phosphate, or phosphonate. Examples of coinpounds falling within this definition are sodium 3-dodecylaminopropionate, sodium 3- dodecylaminopropane sulfonate, dodecyl-beta-alanine, N- alkyltaurines such as the one prepared by reacting dodeclyamine with sodium isethionate according to the teaching of U.S. 2,658,072, N-higher alkyl aspartic acids such as those produced according to the teaching of U.S. 2,438,091, and'the products sold under the trade name Miranol and described in U.S. Patent 2,528,378.

(g) Zwitterionic synthetic detergents can be broadly described as derivatives of aliphatic quaternary ammonium, phosphonium, and sul-fonium compounds, in which the aliphatic radical may be straight chain or branched, and wherein one of the aliphaticsubstituents contains from about 8 to 18 carbon atoms and one contains an anionic water solubilizing group, e.g., carboxy, sulfonate, sulfate, phosphate, or phosphonate. Examples of compounds falling within this definition are 3-(N,N-dimethyl- N-hexadecylammonio) propane-l-sulfonate and 3-(N,N- dimethyl N hexadecylammonia)-2-hydroxy propane-1- sulfonate which are especially preferred for their excellent cool water detergency characteristics.

The alkyl groups contained in said detergent surfactants can be straight or branched and saturated or unsaturated as desired. The above list of detergent surfactants is exemplary and not limiting. Mixtures of the above detergent surfactants can be used.

Examples of suitable fatty amides and alkylolamides include: saturated amides having an acyl group with from 7 to about 22 carbon atoms; N-methyl amides having an acyl group of from about 10 to about 22 carbon atoms; N-isopropanol amides having from about 10 to about 22 carbon atoms; N-isobutyl amides having an acyl group of from about 10 to about 18 carbon atoms; N-ethanol amides having an acyl group of from about 7 to about 22 carbon atoms; N-diethanol amides having an acyl chain of from about 10 to about 22 carbon atoms; unsaturated amides such as oleamide and erucamide; amides of the above types derived from natural oils such as coconut oil, palm oil, tallow, etc; saturated and unsaturated monoand dicarboxylic acid amides with alkyl and aryl groups substituted on the nitrogen, so long as the melting point is between 100 F. and 300 F.; and mixtures thereof. Further examples of such amides and their use in detergent compositions can be found in U.S. Patents 2,383,737; 2,383,738; 2,383,739; 2,383,740.

Suitable fatty alcohols for the purpose of this invention are straight chain and branched, saturated or unsaturated aliphatic alcohols having from about 8 to about 24 carbon atoms, and mixtures thereof. Of especial interest are straight chain primary saturated aliphatic alcohols having 10 to 16 carbon atoms. Typical examples of suitable fatty alcohols are decanol, dodecanol, hexadecanol and eicosanol. Suitable fatty acids are those saturated acids, straight chain or branched, which have from about 16 to about 31 atoms inthe acyl radical, and mixtures thereof. Typical examples of suitable fatty acids are palmitic, stearic, arachidic and behenic acids.

Conventional spray-dried built detergent granules whose particles have the form of hollow beads or fragments of such beads are easily compressible to form smooth abrasion resistant tablets and are suitable for use in the outer layers of the briquettes of the invention. The detergent ingredient in these granules may be, for example an alkyl benzene sulfonate, particularly sodium dodecyl benzene sulfonate. This material has the form of hollow beads or fragments of such beads and is easily compressible to form a smooth, abrasion resistant surface. In the past, such spray-dried synthetic detergent granules have been used to form the whole briquettes and; while briquettes so formed have smooth, abrasion resistant surfaces, they are relatively slow in disintegrating on adding to water.

Built detergent compositions which are produced by dry mixing of a major proportion of particulate inorganic builder salts with detergents do not form smooth surfaces on compression and are not suitable for use as the outer layers of the briquettes, but are suitable for use in the inner layer, as described below.

The mixtures for use as the inner layer of the briquettes of the invention must contain one or more particulate water soluble inorganic detergency builder salts mixed with a particulate detergent composition, the mixture being produced dry or in the presence of insufiicient liquid to destroy the particulate nature of the mixture. Examples of water soluble inorganic alkaline detergency builder salts are alkali metal carbonates, phosphates, polyphosphates, and silicates. Specific examples of such salts are sodium and potassium tripolyphosphates, carbonates, pyrophosphates, phosphates, andhexametaphosphates. The preferred particulate inorganic builder salt is granular sodium tripolyphosphate, especially the hexahydrate, optionally in admixture with solid sodium silicate, in which the ratio SiO :Na O is about 2:1. A solid bleaching agent such as sodium perborate is also preferably included. A very suitable builder mixture consists of sodium tripolyphosphate hexahydrate granules, prepared by granulating the powdered anhydrous salt by spraying on the requisite amount of water while agitating, mixed with solid sodium silicate in which the ratio of siOz Na O is about 2:1, and sodium perborate tetrahydrate.

The particulate detergent composition which is mixed with the particulate inorganic builder salts may be a soap composition, a synthetic detergent composition or a mixed soap-synthetic detergent composition; Examples of the acceptable soap and detergent compounds for this inner layer are the same as those which are listed above as acceptable for the two outer layers. In addition to the active detergent ingredient it may also contain other normal ingredients of detergent compositions such as fatty amides or alkylolamides to enhance the lathering and detergent properties, soil suspending agents such as carboxymethyl cellulose and lime sequestering agents such as nitrilotriacetic acid, ethylene diamine tetraacetic acid and ethane-I-hydroxy-l,1-diphosphonic acid or their salts. It may also contain inorganic salts suchas sodium sulphate which is normally found in association with commercial anionic detergent and some alkaline inorganic builder salts may also be included in the detergent composition (though in general most of the inorganic builder salts are in the particulate inorganic builder salts which is mixed wit-h the detergent composition). The detergent composition must be particulate and is preferably in granular or flake form and may be produced by drying, for example by spray-drying, flash-drying or drumdrying, an aqueous slurry of the detergent and other ingredients.

Generally speaking, of course, the inner layer will contain smaller proportions ofthose functional ingredients in which the outer layers are rich so that the total composition of the briquette represents a balanced built detergent composition suitable for use in domestic washing machines.

The particulate inorganic .builder salts and the particulate detergent composition are mixed together in the absence of liquid or, preferably, in the presence of a small proportion of liquid to serve as binding agent, The proportion of liquid, when used, must not be so great that the particulate nature of the mixture is destroyed. Preferably, the amount of liquid added should not exceed 10% by weight of the composition of the inner layer and, in general, 2 to 3% by weight of liquid is sufiicient. If excess of liquid is added and the mix becomes doughy or pasty, the low T.O.D. which is characteristic of the briquettes of this invention will not be obtained. Preferably, water itself, or an aqueous solution of sodium silicate or an aqueous suspension of starch, is used as the liquid binding agent and this is preferably added as a fine spray during the mixing of the particulate inorganic builder salts and the particulate detergent composition.

The low disintegration times of the briquettes of the invention are due to the inner layer which breaks up rapidly on addition to water. For this reason the inner layer constitutes at least 50%, and preferably 75% to 98%, by weight of the briquette. Particularly suitable briquettes are obtained when the inner layer constitutes from 85% to 95%, by weight, of the briquette. As the inner layer disintegrates on addition to water, the relatively thin outer layers also break up rapidly.

In making the briquettes of the invention the material of one of the outer layers is placed in the die box of a briquetting machine, the material of the inner layer is then superimposed on the first layer and finally the material of the other outer layer is added. The three layers are then compressed together under normal briquetting pressures, preferably 50 to 200 lb. per square inch, to form a three layer briquette. The different layers may be coloured so that the inner and outer layers match or contrast with each other to form an attractive layered briquette.

Example I A briquette was made having an inner layer between two outer layers.

The composition for the inner layer was prepared as follows, all parts being parts by weight:

Detergent flakes made from 4.0 parts of sodium dodecylbenzene sulfonate, 4.9 parts of sodium tallow alkyl sulfate, 0.46 part of lauric acid monoethanolamide, 0.46 part of coconut fatty acid amide, 0.62 part of sodium carboxymethyl cellulose, 0.26 part of tetrasodium ethylene diamine tetraacetate, 6.64 parts of sodium sulfate, 0.5 part of sodium carbonate and 0.36 part of water, by drum-drying an aqueous slurry of these ingredients. 18.2 parts of these flakes were mixed with 57.8 parts of granulated sodium tripolyphosphate hexahydrate, 5.4 parts of sodium silicate power (ratio SiO :'Na O=2:1), 9.0 parts of sodium perborate tetrahydrate and 0.5 part of optical brightening agent. The mixture was sprayed with a suspension of 1.0 part of maize starch in 1.5 parts of water.

The material for the outer layers was spray-dried synthetic detergent granules of the following composition, by weight:

Percent Sodium dodecylbenzene sulfonate 22 Coconut fatty acid monoethanolamide 2 Sodium toluene sulfonate 2 Sodium silicate solids (ratio SiO :Na O=1.6:1) 8 Sodium tripolyphosphate (Na P O 36 Sodium carboxymethyl cellulose 0.5 Sodium sulfate 23 Moisture 6.5

3.4 grams of the spray-dried granules were placed in a 2%" diameter die box of a briquetting machine. 44.2 grams of the inner layer mixture were added and then a final layer of 3.4 grams of spray-dried granules was added. The die was then applied at a pressure of 100 lb. per square inch to form a briquette of 2%" diameter and 51 grams weight.

The briquette had two major surfaces which were smooth and pelasant to handle and which had little tendency to form dust when handled.

To compare the abrasion resistance of the surfaces of the briquettes of the invention with that of other detergent briquettes, the following test method is used:

The briquete is clamped with its major surfaces in the vertical plane. A /z" paint brush is attached to an arm which is driven by an electric motor in reciprocating fashion so that the :brush passes across one major surface of the briquette in a horizontal sweeping stroke. .The dust which is brushed from the surface of the briquette by 50 strokes of this brush is collected and weighed. Tests are carried out on four briquettes and the results are averaged.

In this test, the briquettes of Example 1 produced an average of 0.9 mg. dust compared with 14.1 mg. for a briquette of similar composition but made by compressing dry mixed granular builders and detergent composition, and 27.6 mg. of dust from a commercially available detergent briquette.

To compare the time of disintegration. (T.O.D.) o the briquettes of the invention with other detergent briquettes, the briquette is placed in a plastic salad-washing basket which is then dropped into a Hoover Mk III washing machine containing 8 gallons of water at 130 F. with the machine agitator running. The basket is removed from the water at 5 second intervals and the time of complete disappearance of the briquette is estimated to the nearest 5 seconds. Tests are carried out on 4 briquettes and the average time of disintegration (T.O.D.) is recorded.

In this test the briquettes of Example I had a T.O.D. of 25 seconds compared with 44 seconds for a briquette of similar composition but made by compressing dry mixed granular builders and detergent composition and 88 seconds for a commercially available detergent briquette.

Further examples were prepared following the same procedure as in Example I. In Examples II to V the inner layer had in each case the same composition as the inner layer of Example I. The outer layers had the composition listed in the first sentence of each example.

Example II Flash dried soap granules containing:

Percent Sodium soap of 50% tallow and 50% coconut oil .fatty acids 59.8 Silicate solids 10.3 Trisodium phosphate 3.0 Coconut fatty acid ethanolamide 3.0 Sodium carboxymethyl cellulose 0.5 Sodium perborate 10.0 Moisture 13.4

The briquette had:

Abrasion test mg. of dust 5.6 T.O.D. seconds 32 Example III Powder produced by grating commercial toilet soap comprising sodium tallow soap and 20% of sodium coconut soap.

The briquettes had:

Abrasion test Q mg. of dust 3.4 T.O.D. seconds 26 Example IV Laurie acid monoethanolamide.

The briquettes had:

Abrasion test mg. of dust 1.1 T.O.D. seconds 27 Example V Cetyl alcohol.

The briquettes had: Abrasion test mg. of dust 1.9 T.O.D. seconds 32 In Examples VI to IX, the outer layers had'in each case the same composition as the outer layers of Example I. The inner layers had the composition listed in the first sentence of each example.

Example VI A mixture of 6 parts by weight of anhydrous sodium tripolyphosphate powder and 40 parts by weight of the same spray-dried synthetic detergent granules as were used in the outer layers.

The briquettes had:

Abrasion test mg. of dust 2.0 T.O.D. "seconds" 13 Example VII A mixture of 30 parts by weight of grated toilet soap comprising 80% sodium tallow soap and sodium coconut soap and 70 parts by weight of anhydrous sodium tripolyphosphate powder.

The briquettes had:

Abrasion test mg. of dust" 1.1 T.O.D. seconds 23 Example VIII A mixture of 3-0 parts by weight of the flash-dried soap granules as used for the outer layers of Example II and 70 parts by weight of anhydrous sodium tripolyphosphate powder.

The briquettes had:

Abrasion test mg. of dust 1.9 T.O.D. "seconds" 27 Example IX The composition of the inner layer was the same as for Example I except that 8 parts by weight of soap flakes were used to replace 8 parts by weight of the sodium tripolyphosphate hexahydrate.

The briquettes had:

Abrasion test mg. of dust 2.7 T.O.D. "seconds" In the above examples the outer layers contain, at the most, 36% sodium tripolyphosphate and the inner layers range in sodium tripolyphosphate content from 53.4% to 74.4%. The sodium tripolyphosphate in the outer layers of Example I is calculated on a percentage basis of the total material used in the outer layer. As stated in column 7 at line 58, this figure is 36% sodium tripolyphosphate in Example 1. Examples II through V contain no sodium tripolyphosphate in the outer layers and Examples VI through IX contain 36% sodium tripolyphosphate in the outer layers.

The lower limit of sodium tripolyphosphate in the inner layer is calculated from Example IX wherein 8 parts of soap flakes were substituted for 8 parts of sodium tripolyphosphate hexahydrate in the inner layer composition of Example I. The inner layer composition of Example I contains 93.4 parts by weight, 57.8 parts of which are sodium tripolyphosphate. With the substitution of 8 parts soap in Example IX for 8 parts of sodium tripolyphosphate, 49.8 parts or 53. 4% of sodium tripolyphosphate remain in the inner layer composition. The upper limit for sodium tripolyphosphate in the inner layer composition is derived from Example VI wherein parts anhydrous sodium tripolyphosphate powder and 40 parts spray-dried synthetic detergent granules used for the outer layers in Example I (36% sodium tripolyphosphate) are utilized as the inner layer composition. Therefore, 14.4 part-s of sodium tripolyphosphate (36% 0.4) are added to 6 0 parts of powdered sodium tiripolyphosphate to attain 74.4 parts sodium tripolyphosphate in 1 00 parts of inner layer composition, i.e., 74.4% sodium tripolyphosphate.

I claim:

1. A detergent briquette consisting of three layers wherein the second being the inner layer consists essentially of to 98% by weight of the briquette and wherein the first and third layers being outer layers, consist essentially of the remainder of the briquette, said first and third layers having the same compositions, said first and third layers each consisting essentially of a compressed material which itself consists essentially of at least one ingredient selected from the group consisting of alkali metal soaps, non-soap anionic synthetic detergents, fatty acid alkylol amides, fatty acid amide-s, fatty alcohols, fatty acids, and a mixture of any of these with sodium tripolyphosphate, there being no more than 36% sodium tripolypho-sphate in said compressed material and which, upon compression, produces a relatively smooth abrasion resistant surface, and the second layer being an inner layer of compressed particulate built detergent mixture which consists essentially of a synthetic organic detergent and from 53.4% to 74.4% sodium tripolyphosphate and which would produce, if compressed alone, a rougher and more easily abraded surface than that produced by either of the outer layers, the said inner layer mixture being produced without sufficient liquid being present to destroy the particulate nature of the mixture.

References Cited UNITED STATES PATENTS 1/19 66 Schulerud 252138 1/1930 Stoddard 25293 

